Through the use of formability in thermoplastic resins, various shaped articles have been manufactured. In particular, to impart a high rigidity, a high impact resistance, or a high heat resistance to such a shaped article, it has been proposed that a fibrous filler (e.g., glass fiber) or a scale-like or plate-like inorganic filler (e.g., a talc, and a mica) is added to a thermoplastic resin (e.g., an aromatic polycarbonate resin). In the case of using the fibrous filler, however, the fiber prominence is exhibited in the shaping (or molding) process, and the transferring property to metal mold and the external appearance of the shaped article are deteriorated. Moreover, anisotropy of the fibrous filler tends to cause warps in the shaped article, also deteriorates flowability, and therefore, it is difficult to improve shaping processability (moldability). On the other hand, in the case of reinforcing the shaped article with the scale-like or plate-like inorganic filler, the appearance property (the external appearance) can be improved, however, the reinforcing property is not high. In order to improve rigidity, therefore, it is necessary to use a large amount of the filler. Further, in the case of using these fillers, a strength of weld obtained by merge (or join) of a molten resin composition is low. Accordingly, shaped articles not only being excellent in rigidity, an appearance property, and dimensional stability, but also having high weld strength have been desired.
Japanese Patent Publication No. 2777690 discloses a resin composition which comprises a thermoplastic resin and a wollastonite fiber containing Fe2O3 of 0.2 to 0.5% by weight and Al2O3 of 0.5 to 0.9% by weight as minor constituents; and a resin composition in which the average fiber length of the wollastonite fiber is 20 to 50 μm, the average fiber diameter thereof is 0.05 to 5 μm, and the average aspect ratio thereof is not less than 8 and less than 100. In this document, it is described that a wollastonite fiber without the above properties deteriorates in reinforcing property, or is frangible in kneading with a resin, and that the use of such a resin composition ensures a shaped article having high strength and high elastic modulus and being excellent in surface smoothness and dimensional accuracy.
In this resin composition, however, a usable wollastonite is limited to a specific wollastonite. Further, because the average fiber length of the wollastonite fiber is long, the wollastonite fiber is frangible in kneading with a resin, and cannot impart high reinforcing property to the composition in some cases. Furthermore, even when the wollastonite fiber can reinforce the resin, the composition tends to deteriorate in the weld strength.
Japanese Patent Publication No. 265314 discloses a thermoplastic molding composition which is a mixture of a thermoplastic resin (e.g., a polyalkylene terephthalate, and an aromatic polycarbonate) and an inorganic additive, wherein the inorganic additive is calcium metasilicate in the form of a needle-like fine particle, has a number-average length of 1 to 50 μm and a number-average diameter of 0.1 to 10 μm, and at least 50% thereof are 5 to 25 μm long, and the proportion of the thermoplastic resin relative to the fine particulate inorganic additive is 95/5 to 30/70 (% by weight). This document mentions that the number-average aspect ratio (length/diameter) of the fine-particulate additive is not less than 6, or is in a range of less than 1 to about 10. This document also mentions that the resin composition satisfies properties such as a coated external appearance having high sharpness, or a low coefficient of linear expansion.
However, since the proportion of the fiber having a fiber length of 5 to 25 μm is not less than 50%, it is necessary to use a wollastonite fiber having a sharp (or narrow) distribution in fiber length, and a wide range of a wollastonite fiber cannot be used. Further, as well as the above-cited Japanese Patent Publication No. 2777690, while the addition of the wollastonite fiber imparts reinforced property to a resin, the addition is apt to deteriorate the weld strength. Furthermore, compared with a fibrous filler such as a glass fiber, such a wollastonite fiber can improve the surface appearance of the shaped article, however, the appearance defect of the shaped article occurs to no small extent.
Japanese Patent Application Laid-Open No. 12846/1997 (JP-9-12846A) discloses a resin composition comprising an aromatic polycarbonate resin, an aromatic polyester resin, and a wollastonite having an aspect ratio of 3 to 50, and if necessary an olefinic wax containing a carboxyl group and/or an acid anhydride group. Japanese Patent Application Laid-Open No. 60251/1998 (JP-10-60251A) discloses a blow-moldable resin composition comprising an aromatic polycarbonate resin, an aromatic polyester resin, and a wollastonite having an aspect ratio of 3 to 50, and an olefinic wax containing a carboxyl group and/or an acid anhydride group. Japanese Patent Application Laid-Open No. 324789/1998 (JP-10-324789A) discloses a blow-moldable resin composition comprising an aromatic polycarbonate resin, a graft copolymer (e.g., an ABS resin), a wollastonite having an aspect ratio of 3 to 50, and an olefinic wax containing a carboxyl group and/or an acid anhydride group. These documents also mention that the amount of the olefinic wax is 0 to 7 parts by weight (particular 0.02 to 5 parts by weight) relative to 100 parts by weight of the resin composition.
Japanese Patent Application Laid-Open No. 181497/2001 (JP-2001-181497A) discloses a resin composition which comprises an aromatic polycarbonate-series resin, a thermoplastic aromatic polyester-series polymer, a wollastonite having an aspect ratio (L/D) of 3 to 50, and an olefinic wax having a carboxyl group and/or an acid anhydride group, wherein the proportion of the wollastonite and that of the olefinic wax are 1 to 100 parts by weight and 0.02 to 5 parts by weight, respectively, relative to 100 parts by weight of a mixed resin containing 90 to 50 parts by weight of the aromatic polycarbonate-series resin and 10 to 50% by weight of the thermoplastic aromatic polyester-series polymer.
Further, Japanese Patent Application Laid-Open No. 265769/2002 (JP-2002-265769A) discloses an aromatic polycarbonate resin composition which comprises 100 parts by weight of a resin component containing (1) 50 to 100% by weight of an aromatic polycarbonate resin (A), and (2) 0 to 50% by weight of at least one thermoplastic resin (B) selected from a thermoplastic polyester-series resin (B-1), and a styrene unit-containing resin (B-2) in which the content of the rubber component is less than 40% by weight; and (3) 1 to 100 parts by weight of a wollastonite particle (C) which has such properties of a particle form that a number-average fiber length is not less than 10 μm, a number-average fiber diameter is not less than 4 μm, and a number proportion of a particle having a fiber length of 5 to 25 μm is less than 50%. The document mentions that the resin composition has a high rigidity, a high impact resistance, an excellent surface appearance, and an excellent recycling efficiency. Further, the document mentions a resin composition containing 0.02 to 5 parts by weight of a breaking inhibitor for the wollastonite particle (E) relative to 100 parts by weight of the aromatic polycarbonate resin (A) or resin component, and an olefin wax, as the breaking inhibitor, having a functional group (e.g., carboxyl group, acid anhydride group, and epoxy group) having a reactivity or affinity to the wollastonite particle, and also describes that the weight-average molecular weight of such an olefin wax is 1000 to 20000. In addition, a resin composition containing a flame retardant is disclosed in the document.
In these resin compositions, however, the olefinic wax deteriorates the heat deformation temperature of the compositions, and reduces the heat resistance thereof. Therefore, such compositions seem in no way compatible with thinning and weight saving and improvements of heat resistance, which is required for a recent information equipment (e.g., an information terminal equipment, or an office automation equipment). Moreover, a wollastonite fiber having a short fiber length can improve an appearance property of a shaped article, but deteriorates rigidity of the shaped article, as the above filler. Further, as the number-average fiber diameter of the wollastonite fiber gets larger, the surface property (or surface smoothness) of the shaped article is deteriorated. Thus, usable wollastonite fibers are limited to a specific one.